It is known that shaft furnaces, in particular blast furnaces, are supplied with hot air and with liquid or solid fuels through a circular tuyere fitting in the region of the furnace hearth. These tuyeres are held in place by a tymp accommodated in the interior of the furnace wall, these tymps being extended towards the outside of the wall by a tuyere arch fixed to the outer metal armour of the furnace. The tuyere arches are generally made of steel, while the tymps and the tuyeres are made of copper. The tymps and the tuyeres are, furthermore, water cooled by virtue of a double frustroconical wall.
Whereas the dismounting of a tuyere, which extends beyond the inner side of the furnace wall, generally does not present any particular problems, the dismounting of a tymp is generally a much more difficult operation in view of the fact that the tymp is not only wedged onto the inner seat of the tuyere arch but, in addition, is embedded in the refractory material of the furnace wall, the weight and, if necessary, any relative movement of which it also has to withstand.
The dismounting of a tymp has generally been carried out by a manual service crew, composed of five or six workmen, who try to free the tymp from its seat with the aid of long metal hooks gripping behind the inner edge of the tymp when the tuyere has been disengaged. When the force of manual intervention is insufficient to free the tymp, it is often necessary to resort to a trick consisting of interrupting the circulation of cooling water in the tymp so a to allow it to heat up, due to the heat from the bast furnace wall, beyond the temperature to which it is normally exposed. By suddenly restarting the cooling of the tymp heated up in this way, a thermal shrinkage is produced which may free the tymp from its seat on the tuyere arch. If the fist attempt is not successful, this operation has to be repeated several times, with the risk of seriously damaging the tymp and rendering it unusable, even though it might not necessarily have been considered unusable at the outset. In the extreme case, which occurs more often with reserve tymps than with original tymps, the tymp quite simply has to be gas cut so that it can be disengaged.
There are numerous disadvantages with this mode of operation. Firstly, this work is physically very exhausting for the men of the service crew and, in addition, fairly dangerous. Moreover, many tymps are needlessly damaged, but what is most serious is that the blast furnace remains inoperative for the entire duration of the intervention, which may stretch over several hours.
EP Patent Application No. 90,123,485, corresponding to U.S. Pat. No. 5,127,633, 90,124,485 proposed a device for mounting or dismounting shaft furnace tuyeres or tymps. This is a relatively complex machine provided with a gripper capable of grasping both the tuyere and the tymp and enabling these parts to be freed from their seat without manual force. This gripper is controlled with the aide of a hydraulic unit capable of actuating two telescopic elements of the gripper in opposite directions, as a result of which the hydraulic unit has to be especially designed for this purpose, thereby making the machine relatively complicated and expensive.